[The nucleolus as a possible site of endoplasmic reticulum formation]

Complex investigations of plant and animal cells showed the nucleolus as a compartmental pulsatile system with the cycle of about one hour. Two main constitutions of the nucleolus are revealed by vital cytochemical methods: lipid-positive and lipid-negative ones. A new model of transcription is suggested. According to this model the nucleolus is a place of endoplasmic reticulum formation. The programmed endoplasmic reticulum goes out to the cytoplasm through a special channel just as the nucleolus contracts.